1. Field of the Invention
This invention relates to a thermoplastic resin composition and a graft copolymer, and more particularly to a thermoplastic resin composition incorporating therein a specific graft copolymer and a rigid copolymer, which is excellent in sliding property, surface gloss, surface appearance, and resistance to impacts, and exhibits high weatherability and a graft copolymer using the thermoplastic resin composition as a component and allowing a highly desirable graft copolymer of excellent quality to be produced stably in a high yield.
2. Description of the Prior Art
The graft copolymer obtained by copolymerizing styrene and acrylonitrile with an ethylene-propylene-nonconjugate diene copolymer and the rubber-reinforced resin obtained by mixing this graft copolymer with a copolymer composed of styrene and acrylonitrile called a rigid component have been heretofore known as "AES resin" and, because of their excellence in weatherability, resistance to impacts, and surface gloss, it is expected to find utility in a wide range of applications.
In recent years, in the fields of office machines, household electric appliances, and automobiles, a material of high slidability and self-lubricating property for use in keyboards, bearing materials, gear materials, etc has been required.
Generally, for the impartation of slidability and self-lubricating property to such thermoplastic resins as AES resins, there is adopted the method which comprises adding to the thermoplastic resin a lubricant such as silicone oil and a polyolefin resin such as polyethylene and melting and kneading them. For example, a slidable styrene type resin composition produced by mixing a rubber-modified styrene resin with a polyolefin type resin, a styrene-olefin graft copolymer, and dimethyl silicone (Japanese Patent Application Disclosure SHO 63(1988)-182,361) and a slidable material quality composition produced by melting and kneading a thermoplastic resin with a porous fluorine resin powder (Japanese Patent Application Disclosure SHO 63(1988)-179,965) have been proposed. A specific polyethylene component as an additive for improving the wear resistance of a synthetic resin has been proposed (japanese Patent Application Disclosure SHO 63(1988)-175,069).
The applicant of the present invention developed a method for stably producing a composition by emulsion polymerizing an aromatic vinyl type monomer and a vinyl cyanide type monomer with an ethylene-propylene-non-conjugated diene copolymer rubber latex having a specific gel content and applied this invention for patent under Japanese Patent Application Disclosure SHO 63(1988)-291,913. He also developed a resin composition possessing weatherability and excelling in impact resistance, heatproofness, and surface gloss and filed this invention for patent under Japanese Patent Application Disclosure SHO 63(1988)-291,942 and Japanese Patent Application Disclosure SHO 63(1988)-291,943.
The applicant further developed a method for stably grafting through a specific emulsion polymerization a maleimide type monomer, an aromatic vinyl type monomer, and a vinyl cyanide type monomer onto a modified low molecular weight .alpha.-olefin copolymer-containing ethylene-propylene-nonconjugate diene copolymer-containing cross-linked latex possessing high latex stability. He applied for patent under Japanese Patent Application Disclosure HEI 2(1990)-123,146 an invention concerning a resin composition obtained by the method described above and possessing outstanding heatproofness, rigidity, weatherability, and falling dart impact strength.
The method of the aforementioned conventional technique which incorporates a lubricant such as silicone oil and a polyolefin resin such as polyethylene in a thermoplastic resin by melting and kneading, however, has the disadvantage that the additives defy thorough dispersion and consequently induce impairment of the mechanical strength of the resin, and render it practically difficult to impart outstanding slidability, self-lubricating property, or surface appearance to the produced resin.
The compositions .of Japanese Patent Application Disclosure SHO 63(1988)-291,913, SHO 63(1988)-291,942, and SHO 63(1988)-291,943 excell in weatherability, impact resistance, heatproofness, and surface gloss and yet offer lower slidability than normally required.
The resin composition obtained by the invention of Japanese Patent Application Disclosure HEI 2(1990)-123,146 is excellent in heatproofness, rigidity, weatherability, and falling dart impact strength and yet not fully satisfactory in slidability.